The invention relates to a tool holder for receiving a tool at its tool shaft, comprising a receiving bore for receiving the tool shaft in a predetermined axial position, further comprising a sealing at the inner end of the receiving bore, and a coolant supply from the machine side into a bore of the tool shaft.
Such a prior art is known for example from WO 2005/037484 A2.
To this end a tool holder for receiving a tool at its tool shaft comprises a receiving bore within which the tool shaft is held, a sealing configured as an adjusting screw, whereby the axial position of the tool shaft can be precisely adjusted. To this end the adjusting tool comprises a sealing surface facing the tool to which a respective counter surface at the tool shaft is assigned so that a mechanical sealing is realized. However, such a sealing is only effective when the adjusting screw is pressed against the tool with sufficiently high pressure. If the pressure bias is insufficient, then at the connection between the adjustment screw and the tool a leaky point is generated at which the coolant escapes from the tool holder and is not guided any longer or not guided sufficiently into the bore of the tool shaft.
Such tool holders having an inner passage way for the coolant are used for a so-called minimum quantity lubrification MQL. Herein the coolant is guided through the tool holder and the assigned bore within the tool shaft directly to the working location to effect an effective cooling, or lubrification, respectively, at the working location.
Even when throughout this application only “coolant” is mentioned, than this generally is understood as any kind of coolant or lubrification agent, in liquid, gaseous or mixed form, in particular the form of an aerosol.
Important for a correct functioning of the minimum quantity lubrification MQL is the quality of the sealing between the tool shaft and the adjusting screw, since in case of a leakage a sufficient coolant supply to the tool is not ensured.
Since the tool usually is secured within the receiving bore of the tool holder by force-fit, for instance by thermal shrinkage, either the predetermined axial position of the tool shaft must be correctly determined already during shrinking, or subsequently by setting the adjusting screw an adjusting to the specified nominal dimension must be effected.
However, the necessary pressure bias between the sealing surface of the adjusting screw and the tool shaft is critical and partially depends on the ability of the worker during the tool mounting.
Consequently, in practice again and again insufficiently sealed tools or longitudinally not correctly adjusted tools result.